If your show is established, most of the floor rebooks on site, and you only have a handful of booths to move, a rep on a cut is cheap and fine. The model breaks on a new show or a big expansion, where every booth is a new sale and the rep has no rebooking base to lean on. That is where a dedicated campaign with a built list earns its fee.
In-house works when you already have someone whose whole job is booth sales and attendee outreach. It rarely works when that job is one more thing on a marketer's list, which is the situation most organisers are actually in.
See the detail on exhibitor acquisition and attendee acquisition, or compare the pricing.
Bison Outbound